Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3960 | Thousand metric tons | NA |
| 2004 | 5698 | Thousand metric tons | 43.89% |
| 2005 | 5296 | Thousand metric tons | -7.06% |
| 2006 | 5834 | Thousand metric tons | 10.16% |
| 2007 | 6000 | Thousand metric tons | 2.85% |
